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MEMORANDUM

Subject: Analysis of the Types of Engines Used to Estimate the CAA Section 112(k) Area 

Source Inventory for Stationary Reciprocating Internal Combustion Engines 

From: Melanie King, Energy Strategies Group 

To: EPA Docket EPA-HQ-OAR-2008-0708 

Date: December 21, 2009 

Section 112(c)(3) of the Clean Air Act (CAA) requires that EPA list categories or subcategories 

of area sources sufficient to ensure that area sources representing 90 percent of the area source 

emissions of the 30 HAP that present the greatest threat to public health in the largest number of 

urban areas are regulated. EPA listed the stationary reciprocating internal combustion engine 

area source category under 112(c)(3) and (k) as one of the categories needed to ensure that 90 

percent of such area source emissions are regulated. In response to comments received on the 

proposed NESHAP for existing stationary RICE located at area sources (74 FR 9697), EPA 

analyzed the types of engines that were included in the area source category listing for stationary 

RICE. As a result of this analysis, EPA determined that emissions from existing stationary 

emergency engines located at residential, commercial, and institutional facilities were not 

included in the 1990 baseline emissions inventory that was used as the basis for the listing of 

source categories needed to ensure that 90 percent of area source emissions are regulated.1

 

Residential, commercial, and institutional area source sectors comprise of housing units; 

wholesale and retail businesses; health institutions; social and educational institutions; and 

Federal, state, and local government institutions (e.g., military installations, prisons, office 

buildings). Therefore, EPA determined that these engines at these locations will not be subject 

to this area source standard. A detailed description of the analysis to determine the engines that 

were the basis for the inventory is provided below. 

Summary of the information used in estimating the 1990 112(k) Area Source Inventory for 

Stationary RICE 

The emissions for stationary RICE used to estimate the 1990 112(k) area source inventory were 

calculated using national estimates for fuel consumption (in units of J/yr) of natural gas and 

distillate oil for engines used for two purposes: 

1) engines used by utilities for electricity generation 

2) engines used in industrial applications 

EPA extrapolated fuel consumption information for the year 1990 from estimates of 

consumption for the years 1978 and 1985 in an EPA report (Reference 1). The 1990 fuel 

 

1

 1990 Emissions Inventory of Forty Potential Section 112(k) Pollutants, Supporting Data for EPA’s Section 112(k) 

Regulatory “Strategy. May 21, 1999. 
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consumption estimates were multiplied by a J/Btu conversion and then multiplied by a 

lb/MMBtu emission factor in order to determine the tons emitted per year for each HAP. This 

was done for each fuel type (natural gas and distillate oil). 

The EPA report does not have any further description of what type of engines are included in the 

fuel consumption data. The EPA-RTP Library was able to obtain some of the references for the 

fuel consumption data. None of the references have any information on what size of engines are 

included. The primary references for the 1978/1985 data for the engines used by utilities for 

electricity generation do not provide any additional detail about what engines are included. The 

reference for the 1978 data for the engines used in industrial applications indicates that the data 

is for engines used for the following applications: 

• oil and gas pipelines 

• natural gas processing plants 

• oil and gas exploration 

• crude oil production 

• natural gas production 

• agricultural 

• industrial process 

• municipal water and sewage 

The Library was unable to obtain the reference for the 1985 data for industrial application 

engines. 

Detailed description of fuel consumption data 

The fuel consumption numbers that were used are shown in Table 1. The 1978 and 1985 fuel 

consumption data were obtained from Reference 1. EPA extrapolated the estimates for 1990 

from the 1978 and 1985 estimates. 

Table - Fuel consumption (1015 J/yr) for stationary reciprocating engines 

Year Engines used for electricity 

generation 

Engines used in industrial 

applications 

Natural Gas Distillate Oil Natural Gas Distillate Oil 

1978 25a 31a 1004d 62d

1985 15b 43b 1093e 73e

1990 26c 34c 1171f 72f

a

The 1978 fuel consumption numbers were determined by subtracting National Electric 

Reliability Council (NERC) estimates of 1976 fuel consumption for utility turbines (Reference 2) 

from Federal Power Commission (FPC) data for 1976 fuel consumption by internal combustion 

plants owned by utilities (Reference 3). The 1978 fuel consumption for electricity generation 

reciprocating engines was assumed to be equal to the 1976 numbers “as reciprocating engine 

generating capacity for the two years are about equal.” 

b

The 1985 fuel consumption estimates for reciprocating engines used by utilities for electricity 

generation were determined using NERC estimated fuel requirements for 1985 (Reference 2). 
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The NERC estimates were for fuel consumption for combustion turbines. The 1985 estimates 

were a 40.8% decrease in fuel consumption for gas-fueled turbines from the 1978 figures. The 

EPA report estimated that the fuel consumption for natural gas-fired engines would decrease by 

the same percentage as for turbines (40.8%). Based on estimates from the FPC (Reference 4), 

the EPA report estimated that the total diesel engine capacity would increase by 2.1% from 

1976-1985. The fuel consumption for distillate-fired engines would therefore increase by 37.2% 

from 1978 to 1985 due to the increased capacity and the decreased consumption of natural gas. 

c

The 1990 consumption estimates were “assumed” by Fred Porter of EPA and it doesn’t say how 

he “assumed” those numbers. 

d

The 1978 fuel consumption data for industrial engines was estimated from 1971 fuel 

consumption data from an EPA report (Reference 5) and the ratios of domestic natural gas and 

crude oil production figures for those two years (References 6-8). The 1971 fuel consumption 

data was for engines used in the following applications: 

Application Engine uses listed for application 

Oil and gas pipelines 

Natural gas processing plants drive gas compressors and refrigeration 

compressors 

Oil and gas exploration drive electric generators, drawworks, drilling 

mud pumps, rotary drilling rigs 

Crude oil production drive beam pumps, gas lift compressors, 

hydraulic pump power pumps 

Natural gas production drive repressuring compressors 

Agricultural drive agricultural water pumps 

Industrial process drive industrial process equipment and plant 

air compressors 

Municipal water and sewage drive municipal water and sewage pumps 

e

Projected 1985 fuel consumption rates for industrial internal combustion sources were estimated 

based on 1985 domestic natural gas and crude oil supply rates from the Federal Energy 

Administration (Reference 8). Assumptions used are that fuel consumption rates are 

proportional to domestic natural gas production and that fuel consumption rates for distillate oil 

fueled engines are proportional to domestic crude oil production. Exception is that fuel 

consumed by gas reciprocating engines for crude oil production is assumed to be proportional to 

the domestic crude oil production rate. 

f

Fuel consumption for 1990 was extrapolated for industrial engines assuming that the growth rate 

in fuel consumption from 1978 to 1985 was the same as the growth rate from 1985 to 1990. A 

compound growth rate was assumed. Distribution between gas and oil fired engines was 

assumed to be the same in 1990 as in 1978. 
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References 

1. Emissions Assessment of Conventional Stationary Combustion Systems: Volume II. Internal 

Combustion Sources. EPA-600/7-79-029c. February 1979. 

2. Fossil and Nuclear Fuel for Electric Utility Generation Requirements and Constraints. 1977-

1986. National Electric Reliability Council, Princeton, New Jersey. August 1977. 

3. FPC News Release No. 23009. Federal Power Commission, Washington, D.C. March 25, 

1977. 

4. FPC News Release No. 22673. Federal Power Commission, Washington, D.C. October 15, 

1976. 

5. McGowin, C.R. Stationary Internal Combustion Engines in the United States. Report 

prepared by the Shell Development Co. for the U.S. Environmental Protection Agency. EPA 

Report No. R2-73-210. April 1973. 120 p. NTIS PB-221 457. 

6. 1974 Gas Facts. American Gas Association. Arlington, VA. 1975. 

7. Dupres, W.G., Jr. and J.S. Corsentino. United States Energy through the Year 2000 

(Revised) Bureau of Mines, U.S. Department of the Interior. December 1975. 

8. National Energy Outlook, Federal Energy Administration. February 1976.